Hydrocarbon (HC) vapor traps are used in the air induction path of internal combustion engines to capture hydrocarbon vapors emanating from within the engine, fuel system, pollution control system, and/or related components, and which would otherwise escape into the environment. The HC vapor trap is therefore part of a vehicle's pollution control system, reducing potentially undesired evaporative fuel emissions.
A HC vapor trap includes, as its operative component, an element that adsorbs HC vapors present in an air intake duct and which contact the element. It is known to form an HC-adsorbing element from one or more sheets of paper or polymeric material impregnated with a HC vapor adsorption/desorption material, such as activated carbon. The HC-adsorbing element is located in the engine intake duct to adsorb HC vapors that may be present when the engine is shut down. The HC vapors are then desorbed from the element into the intake airflow when the engine is re-started and fresh air is drawn into the air induction system. The desorbed vapors are carried into the engine along with the air charge and burned.
Numerous methods and structures have been proposed to position a HC trap within/along an engine's air induction path. In a typical installation, a HC trap is located downstream from an air filter box and upstream from an intake plenum and/or intake runners feeding into the cylinders of the engine.
U.S. Pat. No. 8,191,535, owned by the owner of this Application and the disclosure of which is incorporated herein by reference, discloses a HC vapor trap comprising a tubular HC-adsorbing sleeve surrounding a plastic cage. During assembly of the duct, the cage is inserted into the hollow interior of a first duct component through an open end thereof. A second duct component is fastened to the open end of the first component to enclose the trap unit and secure it in its desired installed position.